Method and system for inspecting a pattern

ABSTRACT

The present invention relates to detection of defects with simple specification of the coordinates, in the inspection of an object having a plurality of patterns in which a portion having the two-dimensional repetition and portions having the repetition only in the X direction and in the Y direction are mixedly present. The cross comparison between a notice point and comparison points to for example which are repetitive pitches away from the notice point is carried out, and only the portion having the difference which can be found out with any of the comparison points is extracted as a defect candidate, which results in that the portion having the two-dimensional repetition as well as the portion having the repetition only in the X direction or in the Y direction can be inspected. As a result, while the portion, such as an isolated point, having no repetition both in the X direction and in the Y direction is extracted as the defect candidate, the defect candidate is not treated as the defect in the case where the defect candidate of interest occurs regularly in a plurality of objects to be inspected so that such a defect candidate is excluded to extract only a true defect.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a pattern inspecting method anda system for use in such a method in which an image or a waveformrepresenting the physical properties of an object such as asemiconductor wafer or the like is obtained by utilizing light, anelectron beam or the like, and the image or the waveform is comparedwith the design information or the resultant image, thereby inspecting apattern, and a semiconductor wafer manufacturing method employing thesame.

[0002] As for the conventional method of inspecting a pattern, asdescribed in JP-A-6-294750, there is well known a first method whereinby utilizing the property in which it can be expected that the chipsadjacent to one another have the same pattern, a pattern of one chip iscompared with that of the chip adjacent thereto, and if there is anydifference therebetween, then it is judged that the pattern of any oneof the chips has a defect. In addition, as described in JP-A-57-196530,there is well known a second method wherein by utilizing the property inwhich it can be expected that memory cells within a chip have the samepattern, a pattern of one memory cell is compared with that of thememory cell adjacent thereto, and if there is any differencetherebetween, then it is judged that the pattern of any one of thememory cells has a defect.

[0003] Further, as described in JP-A-3-232250, there is well known athird method wherein a storage unit for storing therein, on the basis ofthe pattern arrangement information within a chip, with respect to thescanning direction of one-dimensional sensor and the storage scanningdirection from the starting point of the chip, the data of a chipcomparison inspection area and a repeated pattern (a pattern of a memorycell) comparison inspection area is included, and with tune to both thesensor scanning position and the stage inspection position, it iscontrolled whether or not the defect output of the chip comparisoninspection and the defect output of the repeated pattern comparisoninspection can be outputted.

[0004] In the conventional first method, two kinds of errors are mixedsince the chips have the different patterns as the objects ofcomparison, and even in the case of the normal portion, the differenceoccurs so that the identification of the defect of interest to the finedefect becomes difficult. The first error is due to the object. Then,the exposure conditions are different between the different chips sincethe aligner can not expose the overall surface of the wafer at the sametime, or in the CVD system or the like, the overall surface of the wafercan be processed at the same time, but if the comparison distance islong, then the different thicknrsses are obtained in the periphery ofthe wafer especially so that the different patterns are formed. Thesecond error is due to the inspection system. Then, while the patternsare detected and compared with one another after a predetermined lapseof time since it is difficult to detect at the same time the large area,if the time interval is long, then the detection and comparison arereadily to be affected by the system drift, the vibration and the like.Therefore, in order to ensure the reliability, the system constructionwill be complicated to increase the cost.

[0005] In the conventional second or third method, the pattern of theobject to be compared is necessarily present. In other words, theinspection area is limited on the division line between the memorieshaving the comparison direction matching that of the inside of thememory mat portion in which the memory cells are regularly arranged, andalso the specification of the area needs to be strictly carried out. Inparticular, in the recent pattern layout in which the inside of thememory mat is finely divided, the inspection areas need to be set inonly the inside of the areas which are obtained by the division. As aresult, it will be expected that the area setting takes a lot of timeand hence the inspection possible area is limited.

SUMMARY OF THE INVENTION

[0006] The present invention was made in order to solve the foregoingproblems associated with the prior art, and it is an object of thepresent invention to provide a pattern inspecting method which iscapable of inspecting all the areas of portions, which are formed bysmall scale repetition, on an object to be inspected such as asemiconductor wafer with high reliability by the simple specification ofthe inspection area, and a system for use in such a method.

[0007] It is another object of the present invention to provide a methodof manufacturing a semiconductor wafer by which for a semiconductorwafer in which a repetitive pattern including both a memory mat portionand a direct peripheral circuit is formed, a defect can be inspectedwith high reliability to enable a high quality semiconductor wafer to bemanufactured.

[0008] In order to attain the above-mentioned objects, according to thepresent invention, there is provided a pattern inspecting method whereinan object to be inspected in which a plurality of same pattern groupsare formed is imaged to obtain two-dimensional digital image signals ofthe object to be inspected; the digital image signals, of the pattern ofthe pattern group to be inspected on the object to be inspected, out ofthe two-dimensional digital image signals are compared with the imagesignals of the patterns of the plurality of other pattern groups on theobject to be inspected which should be essentially the same as thepattern of the pattern group to be inspected in order to extract adefect; and the information relating to the defect thus extracted isoutputted to a communication line.

[0009] In addition, according to the present invention, there isprovided a pattern inspecting method wherein an object to be inspectedin which a plurality of same pattern groups are formed at predeterminedpitches is imaged to obtain image signals of the object to be inspected;the image signal, of the pattern of the pattern group to be inspected onthe object to be inspected, out of the image signals is compared withthe image signals of the other pattern groups on the object to beinspected which should be essentially the same as the pattern of thepattern group to be inspected in order to exclude any of false defectsto detect a true defect; and the information relating to the true defectthus detected is outputted.

[0010] In addition, according to the present invention, there isprovided a method of inspecting a defect of a pattern wherein asemiconductor wafer in which a pattern including both a memory matportion and a direct peripheral circuit is repeatedly formed atpredetermined pitches is imaged; the image signal which has beenobtained by the imaging is converted into digital image signals; thedigital image signals corresponding to a notice point of the pattern tobe inspected on the semiconductor wafer in the digital image signalswhich have been obtained by the conversion are compared with a pluralityof digital image signals corresponding to the positions which are thepredetermined pitches away from the notice point in order to extractdefect candidates; false defects are extracted from the defectcandidates thus extracted; any of the false defects is excluded from thedefect candidates to detect a true defect; and the information relatingto the true defect thus detected is outputted through communicationmeans.

[0011] Further, according to the present invention, there is provided amethod of inspecting a defect of a pattern wherein a semiconductor waferin which a pattern including both a memory mat portion and a directperipheral circuit is repeatedly formed at predetermined pitches isimaged; the image signal which has been obtained by the imaging isconverted into digital image signals; the digital image signalscorresponding to a notice point of the pattern to be inspected on thesemiconductor wafer in the digital image signals which have beenobtained by the conversion are compared with a plurality of digitalimage signals corresponding to a plurality of positions in the peripheryof the notice point, thereby detecting any of defects which are presentin the memory mat portion and/or the direct peripheral circuit of thepattern to be inspected; and the information relating to the defectsthus detected is outputted.

[0012] Further, according to the present invention, there is provided apattern inspection system including: imaging means for imaging an objectto be inspected; A/D conversion means for converting an image signal ofthe object to be inspected which has been imaged by the imaging meansinto digital image signals; defect candidate extracting means forcomparing the digital image signals of a notice point on the object tobe inspected in the digital image signals which have been obtainedthrough the A/D conversion by the A/D conversion means with the digitalimage signals of comparison points, corresponding to the notice point,of a plurality of patterns which should be essentially the same as thepattern of the notice point in order to extract defect candidates of thenotice point; defect detecting means for detecting a true defect fromthe defect candidates thus extracted; and output means for outputtingtherethrough the information relating to the true defect thus dertected.

[0013] Furthermore, according to the present invention, there isprovided a pattern inspection system including: image signal detectingmeans for detecting the physical quantities of an object to beinspected, in which a repetitive pattern is formed, in the form oftwo-dimensional image signals; A/D conversion means for converting thetwo-dimensional image signals which have been detected by the imagesignal detecting means into two-dimensional image signals; differenceimage extracting means for comparing the digital image signals of anotice point in the two-dimensional digital image signals which havebeen obtained through the A/D conversion by the A/D conversion meanswith the digital image signals of a plurality of comparison pointslocated at predetermined pitches which are integral multiples of therepetitive pitches in the X direction and in the Y direction in order toextract the image signals representing the differences (difference imagesignals) between the digital image signals of the notice point and thedigital image signals of the plurality of comparison points; defectcandidate extracting means for extracting defect candidates on the basisof the plurality of difference image signals which have been extractedby the difference image extracting means; and defect extracting meansfor extracting a true defect from the defect candidates which have beenextracted by the defect candidates extracting means.

[0014] By adopting the detection method and the system construction asdescribed above, for all the areas of the portions which are formed bythe small scale repetition of the pattern, any of the defects can beinspected with high reliability by the simple area setting method.

[0015] In addition, by adopting the above-mentioned system construction,for all the areas of the portions which are formed by the small scalerepetition of the pattern, any of the defects can be inspected at highspeed and with high reliability by the simple area setting method.

[0016] Further, by adopting the above-mentioned system construction, forthe semiconductor wafer in which the repetitive pattern including boththe memory mat portion and the direct peripheral circuit is formed, anyof the defects can be inspected with high reliability and hence the highquality semiconductor wafer can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects as well as advantages of the presentinvention will become clear by the following description of thepreferred embodiments of the present invention with reference to theaccompanying drawings, wherein:

[0018]FIGS. 1a and 1 b are schematic views showing the layout of a waferfrom which a semiconductor memory is to be manufactured in accordancewith the present invention, and chips arranged thereon;

[0019]FIG. 2 is a schematic view showing the layout of a memory matportion and a direct peripheral circuit in accordance with the presentinvention;

[0020]FIG. 3 is a schematic view useful in explaining comparison andinspection of the inside of a two-dimensional repetitive pattern inaccordance with the present invention;

[0021]FIG. 4 is a schematic view showing inspection areas in the memorymat portion and the direct peripheral circuit in accordance with thepresent invention;

[0022]FIG. 5 is a schematic view useful in explaining comparison andinspection of the sides of the two-dimensional repetitive pattern inaccordance with the present invention;

[0023]FIG. 6 is a schematic view useful in explaining comparison andinspection of the inside of a one-dimensional repetitive pattern inaccordance with the present invention;

[0024]FIG. 7 is a schematic view useful in explaining comparison andinspection of the ends of a one-dimensional repetitive pattern inaccordance with the present invention;

[0025]FIG. 8 is a schematic view useful in explaining comparison andinspection of the isolated point and the corner portions in accordancewith the present invention;

[0026]FIG. 9 is a schematic structural view showing a first embodimentof a method and a system for inspecting a pattern according to thepresent invention;

[0027]FIGS. 10a to 10 e are schematic views useful in explaining thefeature quantities in accordance with the present invention;

[0028]FIG. 11 is a schematic view useful in explaining a firstmodification of the first embodiment shown in FIG. 9;

[0029]FIG. 12 is a schematic view useful in explaining a secondmodification of the first embodiment shown in FIG. 9;

[0030]FIG. 13 is a schematic structural view showing a second embodimentof the method and the system for inspecting a pattern according to thepresent invention;

[0031]FIG. 14 is a view useful in schematically explaining that in thesecond embodiment of the pattern inspecting method and the system foruse in msuch a method according to the present invention, the shape of adefect is faithfully extracted as the defect candidate;

[0032]FIG. 15 is a schematic structural view showing a third embodimentof the method and the system for inspecting a pattern according to thepresent invention;

[0033]FIG. 16 is a schematic structural view showing a fourth embodimentof the method and the system for inspecting a pattern according to thepresent invention; and

[0034]FIG. 17 is a schematic structural view showing a fifth embodimentof the method and the system for inspecting a pattern according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The preferred embodiments of the present invention willhereinafter be described in detail with reference to the accompanyingdrawings.

[0036]FIG. 1 shows a schematic view of the pattern layout of asemiconductor wafer in the middle of the manufacturing process in asemiconductor memory as an embodiment of an object to be inspectedaccording to the present invention. A large number of chips 2 which willbe finally the products identical to one another are arranged on a wafer1. The pattern layout in the inside of the chips 2 includes, as shown inFIG. 1(b), an indirect peripheral circuit 6 having a very rough pattern,a memory mat portion 3 in which memory cells are two-dimensionallyregularly arranged at repetitive pitches of Px in the X direction and atrepetitive pitches of Py in the Y direction, and a direct peripheralcircuit 4, 5, having a sense amplifier, an I/O circuit, a decordercircuit and the like, which has approximately the same pattern densityas that of the memory mat portion and which is provided in the peripheryof the memory mat portion. The memory mat portion 3 is further finelydivided for every block (on the division line, the repetition is limitedto one direction). The direct peripheral circuit consists of a portion(Y direction direct peripheral circuit) in which the repetion, which ispresent in the X direction of the memory mat portion, is provided onlyin the Y direction and the repetitive pitch is n*Py which is integralmultiples of the repetitive pitch Py of the memory cells, and a portion(X direction direct peripheral circuit) 4 in which the repetition, whichis present in the Y direction of the memory mat portion, is providedonly in the X direction and the repetitive pitch is m*Px which isintegral multiples of the repetitive pitch Px of the memory cells.

[0037] In addition, the memory mat portions 3 and the direct peripheralcircuits 4, 5 are subjected to the grouping every 32 to 128 lines. Then,out of them, since the pattern is formed with a minimum line width ofequal to or smaller than 0.3 μm, the size of the fatal defect is small,and the area in which any of the fine defects should be detected withhigh sensitivity is the memory mat portion 3 and the direct peripheralcircuit 4, 5. Since the indirect peripheral circuit of the area otherthan the area of the memory mat portion 3 and the direct peripheralcircuit 4, 5 has the thick line width, the size of the fatal defect islarge and hence the defect does not need to be necessarily detected withmaximum sensitivity.

[0038] Next, the description will hereinbelow be given with respect tothe basic idea of the present invention for such an object to beinspected. That is, according to the present invention, for a noticepoint 101, there is not prepared only one comparison point 102 but thereare prepared a plurality of comparison points 102 of the subjects ofcomparison, and the image of the notice point 101 is compared with theimages of these compsrison points 102. Then, if the pattern of thenotice point matches the pattern of any one of the comparison pointswith an allowable value, then it is judged that the pattern of thenotice point is not the defect. For example, in the pattern to beinspected shown in FIG. 2, in order to inspect the pattern of the noticepoint 101 represented by the black symbol shown in FIG. 3, this patternis compared with cross-like comparison points 102 a, 102 b, 102 c and102 d each represented by an open symbol as a subject of comparison,i.e., patterns located in the positions each of which is integralmultiples (in the figure, an example of +/−1 times is shown) of therepetitive pitch Qy of the direct peripheral circuit in the Y direction,and patterns located in the positions each of which is integralmultiples (in the figure, an example of +/−1 times is shown) of therepetitive pitch Qx of the direct peripheral circuit in the X direction(first comparison). In this comparison result, if the pattern of thenotice point 101 matches the pattern of any one of the comparison points102 a, 102 b, 102 c and 102 d with an allowable value, then it is judgedthat the pattern of the notice point 102 is not the defect (normalpattern). For example, in the pattern to be inspected like the memorymat portion 3 having the repetition in the X direction and in the Ydirection as shown in FIG. 3, even if the defect is present in any oneof the comparison points 102 a, 102 b, 102 c and 102 d, then the patternof the notice point 101 matches the pattern of any one of the comparisonpoints 102 a, 102 b, 102 c and 102 d, and hence the pattern of thenotice point is judged to be the normal pattern. Then, if the defect ispresent in the notice point 101, then the pattern of the notice point101 mismatches the pattern of any of the comparison points 102 a, 102 b,102 c and 102 d, and hence it can be judged that the defect is presentin the notice point 101. In addition, as shown in FIG. 6, in the patternas well, to be inspected, as the direct peripheral circuit 4, 5 havingthe repetition only in one direction, even if the defect is present inany one of the comparison points 102 a, 102 b, 102 c and 102 d, then thepattern of the notice point 101 matches the pattern of any one of thecomparison points 102 a, 102 b, 102 c and 102 d and hence the pattern ofthe notice point 101 is judged to be the normal pattern. Then, if thedefect is present in the notice point 101, then the pattern of thenotice point 101 mismatches the patterns of the comparison points 102 aand 102 b, and also the pattern of the notice point 101 also mismatchesnormally the patterns of the comparison points 102 c and 102 d. As aresult, it can be judged that the defect is present in the notice point101. However, in the case where the defect is present in the noticepoint 101, and also the pattern of the notice point 101 matches thepatterns of the comparison points 102 c and 102 d since the image of thenotice point 101 has the same variable density level as that of theimages of the comparison points 102 c and 102 d, it can not be judgedthat the defect is present in the notice point 101. That is, there canbe considered the case where the shape of the detected defect varies.Then, the defect can be detected while maintaining the shape of thedefect as much as possible by carrying out the selection of thecomparison results in accordance with the calculation results of thematching degree.

[0039] As a result, with respect to the memory mat portion 3 and thedirect peripheral circuit 4, 5, as shown in FIG. 4, the cross comparisoninspection becomes possible without setting the inspection area exceptfor places 9, such as the corners each having the two-dimensionalrepetitive pattern, each of which has no repetition and each of which isrepresented by the heavy line. While the difference occurs in the place,such as the corner, having no repetition, the place where the differenceoccurs is common to the chips. Hence, these places are compared with oneanother between the chips, and the corner portions are eliminated,thereby enabling these areas to be excluded. On the other hand, thedefect causes the difference in any of the two-stage comparisoninspection (second comparison inspection), and hence can be recognizedas the defect without being excluded.

[0040] In addition, in the above-mentioned comparison, the comparisonemploying the criterion of a plurality of stages is carried out, or theinformation relating to the matching degree is outputted in accordancewith the necessity. This reason is that for the actual wafer, since thealigner for forming a pattern is used near the critical resolution, thefine difference (slightly smaller than 0.1 μm in the current exposuretechnique) occurs in the pattern shape depending on existence andnon-existence of a pattern of the adjacent portion. In the case wherethe size of the defect to be detected is substantially equal to orsmaller than that size, there is the possibility that when the detectionsensitivity is not reduced in the end point of the repetition in whichthere is no pattern in the adjacent portion, this results in the falsereport in which the normal portion is judged to be the defect. Whenemploying the usual criterion, that false report fulfills barely thecriterion and hence is unstable. Then, there is supposed the case wherethat flase report may not occur commonly to all the chips, and hencethere is the possibility that the false report may not be excludedthrough the second comparison. For this reason, in the secondcomparison, the processing in which if the pattern matching is obtainedwithin the allowable range of the first comparison results, then thepattern of interest is not judged to be the defect is carried out forthe criterion of the defect judgement.

[0041] These defect judgement will hereinbelow be described in detailwith reference to FIG. 3, and FIGS. 5 to 8. The pattern (digital imagesignals) of the notice point 101 is compared with the patterns (digitalimage signals) of the comparison points 102 a, 102 b, 102 c and 102 deach of which is at a fixed distance from the notice point 101. In theinside of the portion in which the two-dimensional fixed repetition isobtained as shown in FIG. 3, the pattern of the notice point 101 matchesall the patterns of the comparison points each of which is at a fixeddistance from the notice point 101, and hence it is not judged to be thedefect. In other words, if any defect is present in the pattern of thenotice point 101, then it is detected that the pattern of the noticepoint 101 mismatches all the patterns of the comparison points 102 a,102 b, 102 c and 102 d, and hence the pattern of the notice point 101can be judged to be the defect.

[0042] In the peripheral portion corresponding to the side of theportion having the two-dimensional fixed repetition as shown in FIG. 5,if all the patterns of the comparison points 102 a, 102 b, 102 c and 102d each of which is at a fixed distance from the pattern of the noticepoint 101 are the normal portions, then the pattern of the notice point101 matches all the patterns of the comparison points 102 a to 102 d,and hence the pattern of the notice point 101 is not judged to be thedefect. In other words, if any defect is present in the pattern of thenotice point 101, then it is detected that the pattern of the noticepoint 101 mismatches all the patterns of the comparison points 102 a,102 b, 102 c and 102 d, and hence the pattern of the notice point 101can be judged to be the defect. But, since the pattern of the comparisonpoint 102 c is located in the end of repetition, the size thereof isfinely different from that of the pattern of the notice point 101. Forthis reason, in the comparison of the pattern of the notice point 101with the pattern of the comparison point 102 c, even if the pattern ofthe comparison point 102 c is the normal portion, then a certain degreeof the difference occurs. In the comparison of the pattern of the noticepoint 101 with the pattern of the comparison point 102 a as well as thecomparison of the pattern of the notice point 101 with the pattern ofthe comparison point 102 b, since each of the comparison points 102 aand 102 b is not located in the end of the repetition, if each of thepatterns of the comparison points 102 a and 102 b is the normal portion,then it is expected that the patterns of the comparison points 102 a and102 b are perfectly identical to each other.

[0043] In the portion having the one-dimensional fixed repetition asshown in FIG. 6, the pattern of the notice point 101 matches all thepatterns of the comparison points 102 a and 102 b each of which is at afixed distance from the notice point 101 if all the patterns of thecomparison points 102 a and 102 b are the normal portions. In the end ofthe one-dimensional fixed repetition as shown in FIG. 7, the pattern ofthe notice point 101 matches the pattern of the comparison point 102 awhich ia at a fixed distance from the notice point 101 if the pattern ofthe comparison point 102 a is the normal portion. But, since the patternof the comparison point 102 a is located in the end of the repetition,the size thereof is finely different from that of the notice point 101.For this reason, in the comparison of the pattern of the notice point101 with the pattern of the comparison point 102 a, even if the patternof the comparison point 102 a is the normal portion, then a certaindegree of the difference occurs. In the comparison of the pattern of thenotice point 101 with the pattern of the comparison point 102 c as wellas the comparison of the pattern of the notice point 101 with thepattern of the comparison point 102 d, since each of the comparisonpoints 102 c and 102 d is not located in the end of the repetition, ifeach of the patterns of the comparison points 102 c and 102 d is thenormal portion, then it is expected that the patterns of the comparisonpoints 102 c and 102 d are perfectly identical to each other. Asdescribed above, in both the inside and the side of the two-dimensionalrepetition, and the one-dimensional repetition which have been describedwith reference to FIG. 3, and FIGS. 5 to 7, in any case, the defectportion which is present in the notice point 101 becomes the defectcandidate, and the normal portion does not become the defect candidateat all.

[0044] On the other hand, in the corner portion or the isolated point ofthe two-dimensional fixed repetitive portion as shown in FIG. 8, thepattern of the notice point 101 mismatches all the patterns of thecomparison points 102 a, 102 b, 102 c and 102 d each of which is at afixed distance from the notice point 101 even if all the patterns of thecomparison points 102 a to 102 d are the normal portions, and hence thepatterns of the comparison points 102 a to 102 d become the defectcandidates.

[0045] These defect candidates are subjected to the second comparisoninspection. In the second comparison inspection, the defects which havethe same defect candidate coordinates between the different chips in thecoordinate system having the origin within the chip as the reference andin which the degrees of the pattern matching match one another withinthe allowable range are exculded as the false defects. As a result, thecorner or the isolated point of the two-dimensional fixed repetitiveportion shown in FIG. 8 is excluded so that only the true defect can beextracted.

[0046] In addition, instead of the second comparison inspection, thefalse defects such as the isolated point and the like may be exculded bythe comparison with the information, which is previously obtained, ofthe place having no repetition.

[0047] As described above, the X direction direct peripheral circuit 4is repeatedly formed only in the X direction at repetitive pitches whichare integral multiples (m*Px) of the repetitive pitch of the memorycells, and also the Y direction direct peripheral circuit 5 isrepeatedly formed only in the Y direction at repetitive pitches whichare integral multiples (n*Py) of the repetitive pitch of the memorycells. Therefore, by employing the above-mentioned cross comparison, thecomparison inspection can be commonly carried out with respect to thememory mat portion 3 and the direct peripheral circuit 4, 5.Incidentally, the repetitive pitches (Px, Py) of the memory cells arechanged in accordance with the kind of semiconductor wafer (the kind ofmemory) from which the semiconductor memories as the objects to beinspected will be manufactured. Therefore, it is necessary to change thedistance from the notice point 101 to each of the above-mentionedcross-like comparison points 102 a, 102 b, 102 c and 102 d. However, thefatal fine defect the size of which is equal to or smaller than half theminimum line width (equal to or smaller than 0.3 μm) can be detectedwith high sensitivity without setting the inspection areas with respectto the memory mat portion 3 and the direct peripheral circuit 4, 5.

[0048] The information relating to the detected defect is displayed onthe display means such as a display and also transmitted to otherprocessor such as a computer which manages the whole process through thecommunication line such as the LAN (Local Area Network), and is used asthe data for use in managing the process in combination with the datafrom other inspection system and the process controller.

[0049] A first embodiment of the method and system for inspecting apattern according to the present invention will hereinafter be describedwith reference to FIG. 9. FIG. 9 shows the construction of a firstembodiment of a pattern inspection system. The pattern inspection systemaccording to the present invention includes: electronic opticaldetection means 11 for detecting the physical property of a pattern of awafer 1 as an object to be inspected by the Y direction scanning; astage 12 for moving the wafer 1 in the X direction to form atwo-dimensional image; A/D conversion means 13 for converting atwo-dimensional pattern image signal which has been detected by thedetection means 11 into two-dimensional digital image signals; a delaycircuit 16 for obtaining an image 15 which is obtained bt delaying thetwo-dimensional digital image 14, which has been obtained through theA/D conversion by the A/D conversion means 13, for a fixed time period;storage means (image memory) 17, which is comprised of a two-dimensionalshift register for example, for storing therein the two-dimensionalimage 14 obtained through the A/D conversion by the A/D conversion means13 over a predetermined two-dimensional scanning area; selection means19 for selectively fetching a plurality of images 18 a, 18 b, 18 c and18 d at distances of Dx and Dy, in the positive direction and in thenegative direction, which are integral multiples of the X directionrepetitive pitch Qx and the Y direction repetitive pitch Qy of thedirect peripheral circuit 4, 5, from the images stored in the storagemeans 17; difference image extracting units (difference image extractingmeans) 22 a, 22 b, 22 c and 22 d for comparing an image 15 with images,18 a, 18 b, 18 c and 18 d, respectively, to extract difference images 21a, 21 b, 21 c and 21 d which are used to extract existence andnonexistence of differences therebetween; a defect candidate extractingunit (defect candidate extracting means) 24 a for calculating a defectcandidate image on the basis of the difference images 21 a, 21 b, 21 cand 21 d; a feature quantity extracting unit (feature quantityextracting means) 26 for extracting feature quantities 25 such as thecoordinates of a defect showing the occurence positional information ofthe defect relating to the defect candidate from a defect candidateimage 23, the degree of the pattern mismatching (a difference 62 betweenthe variable density values based on the mismatching of the variabledensity indicated by the slash area in FIG. 10(e) based on thedifference between the variable density values showing a solid shape ofthe defect, an area S (indicated by the slash area in FIG. 10(b)) of thedefect showing the two-dimensional defect size, and the projectionlength Lx in the X direction and the projection length Ly in the Ydirection; a defect extracting unit (defect extracting means) 27 forextracting a true defect on the basis of the feature quantities 25; andgeneral control unit 28 including output means such as a recordingmedium, a printer, display means or the like for controlling the overallsystem. The general control unit 28 outputs the information relating tothe extracted defects, as an output 30, to the communication means (notshown).

[0050] Incidentally, in order to align the wafer 1 as the object to beinspected with which the stage 12 is loaded with the optical axis of thedetection means 11, the alignment marks for exposure which are formed inat least three positions in the periphery of the wafer 1 are imaged byan optical microscope and are converted into an image signal byphotoelectric conversion means. Then, the positions of the threealignment marks are calculated on the basis of the displacement quantityof the stage of the displacement gauge or the laser length measuringdevice included in the stage, and on the basis of the positionalcoordinates of the three alignment marks thus calculated, the wafer 1 isaligned with the optical axis of the detection means 11 with accuracy ofequal to or smaller than 10 μm within one cell with respect to the Xdirection, the Y direction and the rotational (θ) direction. Since withrespect to the rotational direction, the alignment is carried out withaccuracy of equal to or smaller than 10 μm within one cell in the outerperiphery of the wafer, in the cross comparison, the positionaldeviation between the images becomes negligible.

[0051] The above-mentioned electronic optical detection means 11includes, for example: an electron beam source 11 a for emitting anelectron beam; a beam deflector 11 c for scanning the electron beamemitted from the electron beam source 11 a to obtain an image; anobjective lens 11 b for focusing the electron beam on the surface of thewafer as the object to be inspected with a beam diameter of 0.02 to 0.2μm; an ExB 11 d for collecting the secondary electrons generated fromthe wafer to a secondary electron detector 11 b; a focal positioncontrol unit (not shown) for adjusting the focal position between aheight detection sensor 11 f and the objective lens 11 b; and a scanningcontrol unit (not shown) for controlling the beam deflector 11 c torealize the beam scanning. The current of the electron beam is in therange of 10 to 200 nA, the detected picture element size is in the rangeof 0.2 to 0.05 μm on the object to be inspected, and the accelerationvoltage to the object to be inspected is 0.3 kV. The detected pictureelement size needs to be set to a value equal to or smaller than halfthe line width of the pattern of the object to be inspected.

[0052] Incidentally, the above-mentioned electronic optical detectionmeans 11 may be optical image detecting means. In the case of thisoptical image detecting means as well, with respect to the detectedpicture element size, the foregoing is applied thereto.

[0053] Then, the pattern on the wafer 1 is scanned in the positive Xdirection while being scanned with a predetermined scanning width in theY direction from the left-hand side in FIG. 3 for example so that thetwo-dimensional image signal is detected by the electronic opticaldetection means 11 and then is converted into the digital image signalsby the A/D conversion means 13. Then, the mabove-mentioned delay circuit16 delays the digital images outputted from the A/D conversion means 13for a fixed time period until all the digital images of the four pointsincluding the notice point as a subject of the cross comparison havebeen stored in the above-mentioned storage means (image memory) 17. Thatis, the above-mentioned delay circuit 16 delays the scanning quantitybetween the point X and the notice point so that at the time when thedigital image signals of the point X shown in FIG. 3 have been outputtedfrom the A/D conversion means 13, the digital image of the notice point101 is outputted from the delay circuit 16. As a result, the digitalimages with respect to the predetermined two-dimensional scanning areatill the point X shown in FIG. 3 are stored in the storage means 17 onthe basis of a reference address signal 34 obtained from the generalcontrol unit 28. Therefore, since the scanning quantity between thepoint X and the notice point is the known value, by the operation of theselection means 19, on the basis of the desired pitches Dx and Dy whichare selected, in accordance with kind information 35 of the wafer 1inputted from the general control unit 28, from the group of pitches Dxand Dy which are set in the inside of the general control unit 28 withdifferent values for a plurality kind of wafers 1, the addresses of thecomparison points 102 a, 102 b, 102 c and 102 d with respect to theaddress of the notice point 101 are specified to the memory means 17,and the digital image signals of the comparison points 102 a, 102 b, 102c and 102 d are outputted from the storage means 17. Incidentally, thekind information of the wafer 1 may be directly inputted to the generalcontrol unit 28 using input means such as a keyboard, or may be inputtedby reading a symbol, a character, a code or the like which is formed onthe wafer 1 in order to represent the kind of the wafer 1.

[0054] These units and elements operate as follows in order to carry outthe inspection. That is, the pattern of the wafer 1 is detected as thetwo-dimensional image signal by the detection means 11 synchronouslywith the scanning for the stage 12, and then is converted into thedigital image signals by the A/D conversion unit 13, whereby both thedigital image signals 14 and the digital image signals 15 of the noticepoint 101 which have been obtained by delaying the digital image signals14 for the fixed time period. The digital image signals 14 which havebeen obtained at the same time are successively stored in the storagemeans 17 over the predetermined scanning area. Therefore, the digitalimage signals which are already stored in the storage means 17 for thepredetermined scanning area include therein both the digital imagesignals 15 of the notice point 101 which have been obtained by thedelay, and the digital image signals of the comparison points 102 a and102 b which are, in terms of the coordinates, at the distance Dx(corresponding to Dx picture elements) in the positive X direction andin the negative X direction from the digital image signals 15 of thenotice point 101 which are delayed.

[0055] The addresses of the comparison points 102 a and 102 b withrespect to the address of the notice point 101 are specified to thestorage means 17 on the basis of the pitches Dx and Dy which have beenselected by the selection means 19, in accordance with the kindinformation 35 of the wafer 1 outputted from the general control unit28, from the various kinds of pitches Dx and Dy which are previously setin the inside of the general control unit 28, whereby the digital imagesignals 18 a, 18 b, 18 c and 18 d of the comparison points 102 a, 102 b,102 c and 102 d can be read out from the storage means 17 synchronouslywith the digital image signals 15 of the notice point 101 which aredelayed to be extracted (cut out). At this time, the pitches Dx and Dyare respectively set to the values which are integral multiples of the Xdirection repetitive pitch Qx and the Y direction repetitive pitch Qy ofthe direct peripheral circuit 4, 5.

[0056] Next, the difference image extracting units 22 a, 22 b, 22 c and22 d compare the digital image signals 16 of the notice point 101 withthe digital image signals 18 a of the comparison point 102 a, thedigital image signals 18 b of the comparison point 102 b, the digitalimage signals 18 c of the comparison point 102 c and the digital imagesignals 18 d of the comparison point 102 d, respectively, the digitalimage signals 18 a, 18 b, 18 c and 18 d having been extracted, andremove (subtract) the variation allowable value (variable densityallowable value) if brightness based on the fine change of the shapewhen the pattern is normal, the variation allowable value (positionaldeviation allowable value) of brightness due to the positionaldeviation, and the pure noise components, as the comparison parameters,to extract (output) the resultant difference images 21 a, 21 b, 21 c and21 d, respectively. That is, in the case where the difference is equalto or smaller than each of the comparison parameters in each of thedifference images 21 a, 21 b, 21 c and 21 d, it is regarded that thereis no difference (i.e., the difference is “0”) and hence the matching isobtained.

[0057] The defect candidate image extracting unit 24 calculates thedifference image showing the minimum difference (corresponding to thehighest matching) from all the above-mentioned difference images 21 a,21 b, 21 c and 21 d which have been extracted and also calculates thedifference itself, other than the minimum value of the difference whichis “0” (matching), as a defect candidate image signal 23. The featurequantity extracting unit 26 extracts a defect candidate area (defectshape) 61 as shown in FIG. 10(b) from the defect candidate image signal23, and then extracts feature quantities 25 of the defect candidate suchas the mismatching degree showing the solid shape of the defect(corresponding to a difference 62 between the variable density valuesbased on the mismatching of the variable density indicated by the slasharea in FIG. 10(e)), the positional coordinates (e.g., the position G ofthe center of gravity) of the defect area 61 exhibiting the occurrencepositional information of the defect, an area S (indicated by the slasharea in FIG. 10(b)) of the defect area 61 exhibiting the two-dimensionaldefect size, and the projection length Lx in the X direction and theprojection length Lg in the Y direction. Then, these feature quantities15 of the defect candidate are stored in the memory area of the defectextracting unit (defect extracting means) 27 as the processor. Then, thefeature quantities 25 of the defect candidate thus stored are lined upwith the coordinates within the chip. Then, only the defect candidatewhich has, in the fixed range of the coordinates, the mismatching degreelarger than the value which is obtained by adding the allowablethreshold to the mean value of the mismatching degrees, the area largerthan the value which is obtained by adding the allowable thresholdthereto, or the projection length in the X direction and the projectionlength in the Y direction each of which is larger than the value whichis obtained by adding the allowable threshold thereto is extracted asthe true defect. The information relating to the true defect thusextracted is outputted by the output means (a recording medium, aprinter, display means or the like) of the general control unit 28, ortransmitted as an output 30 from the general control unit 28 to acomputer, a server or the like which manages the overall process throughthe communication means such as the LAN (not shown).

[0058]FIG. 10(a) shows a normal wiring pattern 63 for comparison, andFIG. 10(b) shows a wiring pattern 63 in which the defect candidate 61 ispresent. FIG. 10(c) shows a variable density image signal 64 showingbrightness which is obtained from the scanning line a-a shown in FIG.10(a), and FIG. 10(d) shows a variable density image signal 65 showingbrightness which is obtained from the scanning line b-b shown in FIG.10(b). FIG. 10(e) shows the mismatching degree (corresponding to thevariable density values, based on the mismatching, which is indicated bythe slash area) 62 between the variable density image signals 64 and 65.

[0059] In a first modification of the first embodiment, instead of thecross-like comparison, as shown in FIG. 11, the pattern of the noticepoint 101 is compared with the patterns of the two comparison points 102a and 102 c in the X direction and in the Y direction, respectively.This feature is such that while the inspectable area is slightlyreduced, the inspection can be realized with the simple method andsystem construction. That is, in the construction shown in FIG. 9, boththe difference image extracting units 22 b and 22 d can be neglected.

[0060] In a second modification of the first embodiment, instead of thecross-like comparison, as shown in FIG. 12, in addition to thecomparison of the pattern of the notice point 101 with the cross-likepattern of the comparison points, the pattern of the notice point 101 iscompared with the patterns of two comparison points 102 e and 102 farranged in the X direction. This feature is such that it is possible tocope with the case where a plurality of repetitive pitches are present.Likewise, it is considered that a plurality of comparison points areadded in each of the X direction and the Y direction. In the case of thesecond modification, it is necessary to provide additionally differenceimage extracting units 22 e and 22 f.

[0061] According to the first embodiment of the present invention asdescribed above, any defect of only the memory mat portion 3 and thedirect peripheral circuit 4, 5 each having the repetition and bothconstituting the semiconductor memory can be extracted withoutspecifying the coordinates of the inspectable area, and also theinspection can be carried out by setting simply the parameters includingthe distances Dx and Dy between the notice point 101 and the comparisonpoints 102.

[0062] Next, a second embodiment of the method and system for inspectinga pattern according to the present invention will hereinafter bedescribed with reference to FIG. 13. FIG. 13 shows the construction ofthe second embodiment of the pattern inspection system. In the secondembodiment of the pattern inspection system according to the presentinvention, there are added to the first embodiment shown in FIG. 9:matching degree calculating units (matching degree calculating means) 35a, 35 b, 35 c and 35 d for calculating matching degrees Diff a, Diff b,Diff c and Diff d between the digital image signals 15 and the noticepoint 101 and the digital image signals 18 a, 18 b, 18 c and 18 d of thecomparison points 102 a to 102 d and for increasing the allowable valuefor the matching degrees Diff a, Diff b, Diff c and Diff d thuscalculated and for judging the pattern of the notice point to match thepattern of the comparison point of interest, including the vicinitythereof, unless the pattern of the notice point is greatly differentfrom the pattern of the comparison point of interest, to regard each ofthe matching degrees Diff a, Diff b, Diff c and Diff d as “0” (Diff a=0,Diff b=0, Diff c=0 and Diff d=0); and a comparison object selecting unit37 for outputting a selection signal 38 which is used to make selection,in a defect candidate extracting unit 24 b, for judging, that the defectof interest is the defect candidate, from the different images (Comp a)21 a, (Comp b) 21 b, (Comp c) 21 c, and (Comp d) 21 d obtained from thedifference image extracting units (different image extracting means) 22a, 22 b, 22 c and 22 d, in accordance with matching signals 36 a, 36 b,36 c and 36 d which are obtained from the matching degree calculatingunits 35 a, 35 b, 35 c and 35 d, respectively. Incidentally, the digitalimages of the comparison points 102 a to 102 d which are used to extractthe difference images in the difference image extracting units(different image extracting means) 22 a to 22 d may be produced from thedesign information in correspondence to the memory mat portion 3 and thedirect peripheral circuit 4, 5 to be stored in the storage means 17.But, when reading out the digital images of the comparison points 102 ato 102 d, which are produced on the basis of the design information,from the storage means 17, the selection needs to be carried out on thebasis of the selection signal 38 obtained from the comparison objectselecting unit 37.

[0063] The matching calculating units 35 a, 35 b, 35 c and 35 d cut out,approximately similarly to the difference image extracting units(difference image extracting means) 22 a to 22 d, the difference imagesDiff a, Diff b, Diff c and Diff d, which have been obtained by removing(subtracting) the comparison parameters therefrom, every picture elementmamery range of 5×5 for example. Then, each of the matching degreecalculating units 35 a to 35 d sets the data relating to the minimumdifference image in the picture element memory range of 5×5 thus cut outas the value of the central picture element to subject the differenceimage signal represented by the approximate matching (i.e., the variabledensity difference is smallest in the picture element memory range of5×5; the minimum difference image) to the two-dimensional enlargementprocessing. Then, each of them digitizes the resultant difference imagesignal with the large threshold, and obtains the matching unless themagnitude of the resultant difference image signal exceeds that largethreshold, and also outputs surely, as the matching, the data relatingto both the comparison point the pattern of which is not greatlydifferent from the pattern of the notice point, and its vicinity (withinthe picture element memory range of 5×5). That is, each of the matchingdegree calculating units 35 a, 35 b, 35 c and 35 d increases theallowable value (the threshold) and regards the patterns of the noticepoint and the comparison point as the matching unless the pattern of thenotice point is greatly different from the pattern of the comparisonpoint including its vicinity to output the matching signal. As a result,the comparison object selecting unit 37 can judge, even if the finedefect is present, whether the notice point 101 is in the state of thetwo-dimensional repetition, in the state of the repetition in thehorizontal (X) direction, in the state of the repetition in the vertical(Y) direction, in the state of the end of the repetition, or in thestate of the isolated point. More specifically, at the time when thefour matching degree calculating units 35 a, 35 b, 35 c and 35 d haveoutputted the matching signals (Diff a to Diff d=0), the comparisonobject selecting unit 37 judges that the notice point 101 is in thestate of the two-dimensional repetition, and then outputs the selectionsignal to the defect candidate extracting unit 24 b so that the defectcandidate extracting unit 24 b outputs the minimum value (min (Comp a toComp d)) of the four difference images (Comp a to Comp d) as the defectcandidate. In addition, at the time when both the matching degreecalculating units 35 a and 35 b out of the four matching degreecalculating units 35 a, 35 b, 35 c and 35 d have outputted the matchingsignals (Diff a=0, Diff b=0), the comparison object selecting unit 37judges that the notice point 101 is in the state of the repetition inthe horizontal (X) direction and then outputs the selection signal tothe defect candidate extracting unit 24 b so that the defect candidateextracting unit 24 b outputs the minimum value (min (Comp a, Comp b)) ofthe two difference images (Comp a, Comp b) in the horizontal (X)direction out of the four difference imasges as the defect candidate. Inaddition, at the time when both the matching degree calculating units 35c and 35 d out of the four matching degree calculating units 35 a, 35 b,35 c and 35 d have outputted the matching signals (Diff c=0, Diff d=0),the comparison object selecting unit 37 judges that the notice point 101is in the state of the repetition in the vertical (Y) direction and thenoutputs the selection signal to the defect candidate extracting unit 24b so that the defect candidate extracting unit 24 b outputs, as thedefect candidate, the minimum value (min (Comp c, Comp d)) of the twodifference images (Comp c, Comp d) in the vertical (Y) direction out ofthe four difference images. In addition, at the time when only any oneof the four matching degree calculating units 35 a, 35 b, 35 c and 35 dhas outputted the matching signal (only Diff a is 0, only Diff b is 0,only Diff c is 0, or only Diff c is 0), the comparison object selectingunit 37 judges that the notice point 101 is in the state of the end ofthe repetition and then outputs the selection signal to the defectcandidate extracting unit 24 b so that the defect candidate extractingunit 24 b outputs, as the defect candidate, the difference image itself(Comp a, Comp b, Comp c, or Comp d), which has been judged to be the endpoint, out of the four difference images. Further, at the time when thefour matching degree calculating units 35 a, 35 b, 35 c and 35 d haveoutputted the mismatching signals (Diff a to Diff d=0), the comparisonobject selecting unit 37 judges that the notice point 101 is in thestate of the isolated point and then outputs the selection signal to thedefect candidate extracting unit 24 b so that the defect candidateextracting unit 24 b outputs, as the defect candidate, the minimum value(min (Comp a to Comp d)) of the four difference images (Comp a to Compd). As a result, the defect candidate extracting unit 24 b outputs, asthe defect candidate, the minimum value (min (Comp a to Comp d)) of thefour difference images (Comp a to Comp d) when the notice point 101 isin the state of the two-dimensional repetition, outputs, as the defectcandidate, the minimum value (min (Comp a, Comp b)) of the twodifference images (Comp a, Comp b) in the horizontal (X) direction whenthe notice point 101 is in the state of the repetition in the horizontal(X) direction, outputs, as the defect candidate, the minimum value (min(Comp c, Comp d)) of the two difference images (Comp c, Comp d) in thevertical (Y) direction when the notice point 101 is in the state of therepetition in the vertical (Y) direction, outputs, as the defectcandidate, the difference image itself (Comp a, Comp b, Comp c, or Compd), which is judged to be the end point, when the notice point 101 is inthe state of the end point of the repetition, and outputs, as the defectcandidate, the minimum value (min (Comp a to Comp d)) of the fourdifference images (Comp a to Comp d) when the notice point 101 is in thestate of the isolated point. Then, the processings in the featureextracting unit (feature extracting means) 26 and the defect extractingunit (defect extracting means) 27 are the same as these in the firstembodiment of the pattern inspection system shown in FIG. 9.

[0064] In the first embodiment of the pattern inspection system shown inFIG. 9, the defect candidate image extracting unit 24 a outputs, as thedefect candidate image signal 23, the difference image exhibiting theminimum value (exhibiting the most matching degree) of the difference(mismatching) out of all the difference images 21 a, 21 b, 21 c and 21d. In this case, as schematically shown in FIG. 14, while the datarelating to a fine defect 141 is outputted as the defect candidatesignal without losing its contour (which has the fine stepped portion sothat the large change occurs in the variable density signal) 142, thereis the possibility that the pattern of a flat portion 143 of the finedefect 141 may match the pattern of the comparison point 102 d to belosed. As a result, there is also the possibility that the defectcandidate signal may be outputted in which the shape of the fine defectis changed. In particular, in the case where the fine defect 141 is thelack defect, it is considered that the image of the notice point 101having the fine defect may match the image of the pattern of thecomparison point 102 d having no repetition. As a result, in the firstembodiment, the possibility that the situation may occur in which onlythe contour of the fine defect 141 is extracted is large.

[0065] However, in the second embodiment of the pattern inspectionsystem shown in FIG. 13, the data relating to the defect itself can befaithfully outputted as the defect candidate signal 23 without changingthe shape and the like of the defect, and hence as compared with thefirst embodiment, the highly reliable inspection of the fine defect canbe realized on the basis of the cross comparison.

[0066] Next, a third embodiment of the method and system for inspectinga pattern according to the present invention will hereinafter bedescribed with reference to FIG. 15. FIG. 15 shows the third embodimentof the pattern inspection system. In the third embodiment of the patterninspection system according to the present invention, a point ofdifference in construction from the first embodiment of the patterninspection system shown in FIG. 9 is that the difference image 21 abetween the notice point 101 and the comparison point 102 a which isoutputted from the difference image extracting unit 22 a is obtained bydelaying the difference image obtained from the difference imageextracting unit 22 b for a time period required for scanning thedistance from the notice point 101 to the comparison point 102 a in theX-direction scanning when detecting the image, using a delay circuit 29a constituted by a 1-raster shift resister and the like for example.When the data relating to the difference image 21 a is outputted fromthe delay circuit 29 a, naturally, the data of the difference image 21 bbetween the notice point 101 and the comparison point 102 b is outputtedfrom the difference image extracting unit 22 b. That is, the informationof both the difference images 21 a and 21 b described in the firstembodiment is included in the difference image obtained from thedifference image extracting unit 22 b. The difference image 21 b isobtained by comparing the notice point 101 with the comparison point 102b which is at a distance of the picture elements corresponding to Dxfrom the notice point 101 in the positive X direction, while thedifference image 21 a is obtained by comparing the notice point 101 withthe comparison point 102 a which is at a distance of the pictureelements corresponding to Dx from the notice point 101 in the negative Xdirection. In other words, if in the difference image 21 a, the noticepoint is substituted for the comparison object, then the differenceimage 21 a becomes equal to the image which is obtained by shifting thedifference image 21 b by the picture elements corresponding to Dx in thenegative X direction.

[0067] In addition, the difference image 21 c between the notice point101 and the comparison point 102 c which is outputted from thedifference image extracting unit 22 c is obtained by delaying thedifference image obtained from the difference image extracting unit 22 dfor a time period required for scanning the distance from the noticepoint 101 to the comparison point 102 c in the Y-direction scanning whendetecting the image, using a delay circuit 29 c which is, for example,constituted by arranging a large number of 1-raster shift register inthe Y direction. When the data relating to the difference image 21 c isoutputted from the delay circuit 29 c, naturally, the data relating tothe difference image 21 d between the notice point 101 and thecomparison point 102 d is outputted from the difference image extractingunit 22 d. That is, the information of both the difference images 21 cand 21 d is, likewise, included in the difference image obtained fromthe difference image extracting unit 22 d. The difference image 21 d isobtained by comparing the notice point 101 with the comparison point 102d which is at a distance of the picture melements corresponding to Dyfrom the notice point 101 in the positive Y direction, while thedifference image 21 c is obtained by comparing the notice point 101 withthe comparison point 102 c which is at a distance of the pictureelements corresponding to Dy from the notice point 101 in the negative Ydirection. In other words, if in the difference image 21 c, the noticepoint is substituted for the comparison object, then, the differenceimage 21 c becomes equal to the image which is obtained by shifting thedifference image 21 d by the picture elements corresponding to Dy in thenegative Y direction.

[0068] However, there is the case where the distances from the noticepoint to the X direction and Y direction compasrison points are changeddepending on the kind of wafer 1 as the object to be inspected.Therefore, the delay times in the delay circuits 29 a and 29 c need tobe changed on the basis of the information of the distances from thenotice point 101 to the X direction and Y direction compasrison points102 which information is obtained from the selection means 19.

[0069] As described above, similarly to the first embodiment shown inFIG. 9, the number of difference image extracting units required forcarrying out the complicated processing such as the extraction of thecomparison parameters is reduced by half as compared with the firstembodiment and also the delay circuits each having the simpleconfiguration are merely provided, whereby any defect in only the memorymat portion 3, the x direction direct peripheral circuit 4 and the Ydirection direct peripheral circuit 5 each having the repetition can beextracted without specifying the coordinates of the inspection possiblearea, and also the inspection can be carried out on the basis of thesimple parameter setting.

[0070] It will be apparent that the third embodiment can be naturallyapplied to the above-mentioned second embodiment.

[0071] Next, a fourth embodiment of the method and system for inspectinga pattern according to the present invention will hereinafter bedescribed with reference to FIG. 16. FIG. 16 shows the fourth embodimentof the pattern inspection system. In the fourth embodiment of thepattern inspection system according to the present invention, a point ofdifference from the third embodiment of the pattern inspection systemshown in FIG. 15 is that instead of the defect extracting unit 27, thereare provided: an isolated point storage unit 31 for storing previouslytherein the coordinates of the place having no repetition; and acoordinate comparison unit 32 for excluding any of defects, out of thedefect candidates, having the coordinates matching the coordinateinformation of the place having no repetition, which coordinateinformation is previously stored, to extract the true defect. Thiscoordinate comparison unit 32 has the same function as that of thedefect extracting unit 27 in the first to third embodiments.

[0072] Then, the feature quantity extracting unit 26 extracts, as shownin FIG. 10(b), the defect candidate area (defect shape) 61 from thedefect candidate image 23, and also extracts the feature quantities 25of the defect candidate such as the mismatching degree (corresponding tothe difference 62 between the variable density values based on themismatching of the variable density indicated by the slash area in FIG.10(e)) exhibiting the solid shape of the defect, the positioncoordinates (e.g., the position G of the center of gravity) of thedefect area 61 exhibiting the occurrence positional information of thedefect, the area S (indicated by the slash area in FIG. 10(b)) of thedefect area 61 exhibiting the two-dimensional size of the defect, andthe projection length Lx in the X direction and the projection length Lyin the Y direction. These feature quantities 15 of the defect candidatearea stored in the memory area of the coordinate comparison unit 32 asthe processor. In the coordinate comparison unit 32, the featurequantities 25 of the defect candidate thus stored are lines up with thecoordinates within the chip on the basis of the position coordinates(e.g., the position G of the center of gravity) of the defect area 61showing the occurrence position information of the defect. Then, any ofthe defect candidates the coordinates of which match, in the fixedcoordinate range for example, the coordinates of the isolated pointwhich are previously stored in the coordinate storage unit 31 isexcluded to extract only the true defect. The information relating tothe true defect thus extracted is outputted through the output means (arecording medium, a printer, display means or the like) or transmittedto the computer which manages the overall process through the network.

[0073] Incidentally, the coordinate data of the isolated point which ispreviously stored in the coordinate storage unit 31 may be registrated,in the form of the design information of the inspection object, theplace which is registrated on the basis of the inspection by the worker,or the combination thereof, using the input means which is, for example,provided in the general control unit 28.

[0074] In the fourth embodiment as well, by applying the firstmodification of the first embodiment thereto, the second comparisoninspection is carried out, and the coordinates of the false defectswhich can be excluded are registrated in order to exclude them. As aresult, the coordinates to be registrated can be specified to thecoordinate storage unit 31 with the less number of processes.

[0075] According to the fourth embodiment, since the coordinates of anyof the defect candidates are compared with the coordinates which arepreviously stored, any of the false defects can be surely excluded.

[0076] Naturally, it will be apparent that the fourth embodiment can beapplied to ,the above-mentioned first and second embodiments as well.

[0077] Next, a fifth embodiment of the method and system for inspectinga pattern according to the present invention will hereinafter bedescribed with reference to FIG. 17. FIG. 17 shows the fifth embodimentof the pattern inspection system. A point of difference of the fifthembodiment from the first embodiment is that there are provided: storagemeans 201 for storing therein the data of the images 14 after the A/Dconversion which are used to detect a defect candidate image 206 basedon the chip comparison; selection means 202 for fetching selectively theimage 207 at a distance backwardly which is integral multiples of thechip, from the images stored in the storage means 201; image processingmeans 203 for comparing the currently detected image 14 with the image207, selected by the selection means 202, at a distance backwardly whichis integral multiples of the chip to calculate the defect candidateimage 206; and defect candidate selecting means 204 for selecting boththe defect candidate image 23 based on the cross comparison which isobtained from the defect candidate extracting means 24 and the defectcandidate image 206 of the chip comparison, on the basis of thecoordinate data of the inspection place which is obtained in the generalcontrol unit 28.

[0078] The defect candidate image extracting means 24 calculates theminimum value (the difference image having the most matching) over thedifferent images 21 a, 21 b, 21 c and 21 d which have been extracted inthe difference image extracting means 22 a to 22 d, respectively,thereby calculating the defect candidate image 23 based on the crosscomparison.

[0079] On the other hand, both the image before one chip and the digitalimage 14 which are previously stored in the storage means 201 aresubjected to the image processing to calculate the defect candidateimage 206 bases on the chip comparison. The defect candidate selectingunit 204 receives both the defect candidate image 23 based on the crosscomparison and the defect candidate image 206 based on the chipcomparison to fetch a defect candidate image 208 which has been selectedon the basis of the candidate data of the area of the memory mat portion3 and the direct peripheral circuit 4, 5 on the chip and the area of thedirect peripheral circuit 6 thereon. That is, the defect candidateselecting unit 204 selects the defect candidate image 23 based on thecross comparison with respect to the area of the memory mat portion 3and the direct peripheral circuit 4, 5 on the chip, and selects thedefect candidate image 206 based on the chip comparison with respect tothe area of the indirect peripheral circuit 6 on the chip to output thedefect candidate image thus selected as the defect candidate image 208.

[0080] The feature quantity extracting unit 26 extracts the defectcandidate area (defect shape) 61 as shown in FIG. 10(b) from the defectcandidate images 208 thus selected, and also extracts the featurequantities 25 of the defect candidate such as the mismatching degree(corresponding to the difference 62 between the variable density valuesbased on the mismatching of the variable density indicated by the slasharea in FIG. 10(e), the position coordinates (e.g., the position G ofthe center of gravity) of the defect area 61 exhibiting the occurrenceposition information of the defect, the area S (indicated by the slasharea in FIG. 10(b)) of the defect area 61 exhibiting the two-dimensionalsize of the defect, and the projection length Lx in the X direction abdthe projection length Ly in the Y direction. These feature quantities 15of the defect candidate are then stored in the memory area of thefeature extracting unit 26 as the processor. Then, the featureextracting unit 26 lines up the feature quantities 25 of the defectcandidate thus stored with the coordinates within the chip, and alsoextracts, as the true defect, only the defect candidate having themismatching degree larger than the level which is obtained by adding theallowable threshold to the mean value of the mismatching degree, withina fixed coordinate range for example. Incidentally, the defect candidateselecting unit (defect candidate selecting means) 204 selects, on thebasis of the coordinate data of the inspection place, the defectcandidate image 23 based on the cross comparison in the case of thememory mat portion 3, the X direction direct peripheral circuit 4 andthe Y direction direct peripheral circuit 5 each having the repetition,and selects the defect candidate image 206 based on the chip comparisonin the case of other indirect peripheral circuit 6.

[0081] According to the fifth embodiment, the inspection can be carriedout with the combination of the cross comparison and the chipcomparison, and also any of the defects in the indirect peripheralcircuit 6 as well as any of the defects in the memory mat portion 3, theX direction direct peripheral circuit 4 and the Y direction directperipheral circuit 5 each having the repetition can be detected.

[0082] Naturally, it will be apparent that the fifth embodiment can beapplied to the above-mentioned second, third and fourth embodiments aswell.

[0083] While in all the first to fifth embodiments as described above,the description has been given with respect to the case of the systememploying the electronic optical detection means, it is to be understoodthat even in the system employing any of detection means such as opticaldetection means, all the embodiments can be implemented similarly.

[0084] According to the present invention, by the simple specificationof the inspection area, the highly reliable inspection can be carriedout.

[0085] In addition, according to the present invention, by the simplespecification of the inspection area, the defects in all the areas eachhaving the small scale repetition can be inspected at high speed andwith high reliability.

[0086] In addition, according to the present invention, for thesemiconductor wafer in which the memory mat portion and the directperipheral circuit each having the repetitive pattern are formed, any ofthe defects can be inspected with high reliability so that the highquality semiconductor wafer can be manufactured.

[0087] While the present invention has been particularly shown anddescribed with reference to the preferred embodiments and the specifiedmodifications thereof, it will be understood that the various changesand other modifications will occur to those skilled in the art withoutdeparting from the scope and true spirit of the invention. The scope ofthe invention is therefore to be determined sololy by the appendedclaims.

1. A method of inspecting a pattern wherein an object to be inspected inwhich a plurality of same pattern groups are formed is imaged to obtaintwo-dimensional digital image signals of the object to be inspected; thedigital image signals, of the pattern of the pattern group to beinspected on the object to be inspected, out of the two-dimensionaldigital image signals are compared with the image signals of thepatterns of the plurality of other pattern groups on the object to beinspected which should be essentially the same as the pattern of thepattern group to be inspected in order to extract a defect; and theinformation relating to the defect thus extracted is outputted to acommunication line.
 2. A pattern inspecting method according to claim 1,wherein the plurality of other pattern groups are the pattern groupswhich are adjacent to the pattern group to be inspected.
 3. A patterninspecting method according to claim 1, wherein the plurality of otherpattern groups are the pattern groups which are perpendicularly adjacentto the pattern group to be inspected.
 4. A pattern inspecting methodaccording to claim 1, wherein when the digital image signals of thepattern of the pattern group to be inspected on the object to beinspected do not match any of the image signals of comparison patternsof a plurality of other pattern groups, on the object to be inspected,each of which is expected to have the same pattern as that of thepattern group to be inspected, the pattern of the pattern group to beinspected is selected as a defect candidate, and a true defect isextracted from the defect candidates thus selected.
 5. A method ofinspecting a pattern wherein an object to be inspected in which aplurality of same pattern groups are formed at predetermined pitches isimaged to obtain image signals of the object to be inspected; the imagesignal, of the pattern of the pattern group to be inspected on theobject to be inspected, out of the image signals is compared with theimage signals of the other pattern groups on the object to be inspectedwhich should be essentially the same as the pattern of the pattern groupto be inspected in order to exclude any of false defects to detect atrue defect; and the information relating to the true defect thusdetected is outputted.
 6. A pattern inspecting method according to claim5, wherein defect candidates of the pattern of the pattern group to beinspected are extracted on the basis of the differences between theimage signal of the pattern of the pattern group to be inspected on theobject to be inspected and the image signals of the patterns of theother pattern groups; the defect candidates thus extracted are comparedwith the pattern group to extract any of the false defects; and thefalse defects are excluded from the defect candidates to detect the truedefect.
 7. A pattern inspecting method according to claim 5, wherein thedefects which appear regularly over a plurality of pattern groups areexcluded as the false defects from the defect candidates which have beenextracted by comparing the image signal of the pattern of the patterngroup to be inspected on the object to be inspected with the imagesignals of the patterns of the other patterns, on the object to beinspected, which should be essentially the same as the pattern of thepattern group to be inspected, thereby detecting the true defect.
 8. Amethod of inspecting a defect of a pattern wherein a semiconductor waferin which a pattern including both a memory mat portion and a directperipheral circuit is repeatedly formed at predetermined pitches isimaged; the image signal which has been obtained by the imaging isconverted into digital image signals; the digital image signalscorresponding to a notice point of the pattern to be inspected on saidsemiconductor wafer in the digital image signals which have beenobtained by the conversion are compared with a plurality of digitalimage signals corresponding to the positions which are the predeterminedpitches away from the notice point in order to extract defectcandidates; false defects are extracted from the defect candidates thusextracted; any of the false defects is excluded from the defectcandidates to detect a true defect; and the information relating to thetrue defect thus detected is outputted through communication means.
 9. Apattern defect inspecting method according to claim 8, wherein thedefects, out of the defect candidates which have been extracted, whichappear regularly on said semiconductor wafer are extracted as the falsedefects.
 10. A method of inspecting a defect of a pattern wherein asemiconductor wafer in which a pattern including both a memory matportion and a direct peripheral circuit is repeatedly formed atpredetermined pitches is imaged; the image signal which has beenobtained by the imaging is converted into digital image signals; thedigital image signals corresponding to a notice point of the pattern tobe inspected on said semiconductor wafer in the digital image signalswhich have been obtained by the conversion are compared with a pluralityof digital image signals corresponding to a plurality of positions inthe periphery of the notice point, thereby detecting any of defectswhich are present in said memory mat portion and/or said directperipheral circuit of the pattern to be inspected; and the informationrelating to the defects thus detected is outputted.
 11. A patterninspection system comprising: imaging means for imaging an object to beinspected; A/D conversion means for converting an image signal of theobject to be inspected which has been imaged by said imaging means intodigital image signals; defect candidate extracting means for comparingthe digital image signals of a notice point on the object to beinspected in the digital image signals which have been obtained throughthe A/D conversion by said A/D conversion means with the digital imagesignals of comparison points, corresponding to the notice point, of aplurality of patterns which should be essentially the same as thepattern of the notice point in order to extract defect candidates of thenotice point; defect detecting means for detecting a true defect fromthe defect candidates thus extracted; and output means for outputtingtherethrough the information relating to the true defect thus dertected.12. A pattern inspection system according to claim 11, wherein saiddefect candidate extracting means includes: difference image extractingunits for extracting difference images between the digital image signalsof the notice point and the reference image signals of comparisonpoints, corresponding to the notice point, of the plurality of patternswhich should be essentially the same as the pattern of the notice point;and a defect candidate extracting unit for comparing the differenceimages which have been extracted by said difference image extractingunits with a preset value to extract the defect candidates.
 13. Apattern inspection system according to claim 11, wherein said defectdetecting means includes: a feature quantity extracting unit forextracting feature quantities of the defect candidates which have beenextracted by said defect candidate extracting means; and a defectextracting unit for detecting a true defect on the basis of the featurequantities of the defect candidates which have been extracted by saidfeature quantity extracting unit.
 14. A pattern inspection systemcomprising: image signal detecting means for detecting the physicalquantities of an object to be inspected, in which a repetitive patternis formed, in the form of two-dimensional image signals; A/D conversionmeans for converting the two-dimensional image signals which have beendetected by said image signal detecting means into two-dimensional imagesignals; difference image extracting means for comparing the digitalimage signals of a notice point in the two-dimensional digital imagesignals which have been obtained through the A/D conversion by said A/Dconversion means with the digital image signals of a plurality ofcomparison points located at predetermined pitches which are integralmultiples of the repetitive pitches in the X direction and in the Ydirection in order to extract the image signals representing thedifferences (difference image signals) between the digital image signalsof the notice point and the digital image signals of the plurality ofcomparison points; defect candidate extracting means for extractingdefect candidates on the basis of the plurality of difference imagesignals which have been extracted by said difference image extractingmeans; and defect extracting means for extracting a true defect from thedefect candidates which have been extracted by said defect candidatesextracting means.
 15. A pattern inspection system according to claim 14,wherein said defect extracting means detects, as the true defect, thedefect candidate in the case where the defect candidate if interestwhich has been extracted by said defect candidate extracting meansoccurs irregularly on the object to be inspected.
 16. A patterninspection system according to claim 15, wherein said difference imageextracting means includes storage means for storing therein the digitalimage signals of at least the plurality of comparison points in thetwo-dimensional digital image signals which have been obtained throughthe A/D conversion by said A/D conversion means.
 17. A patterninspection system according to claim 15, wherein said defect extractingmeans includes feature quantity extracting means for extracting thefeature quantities of the defects from the defect candidates.